In the development of high strength iron alloys, it is generally accepted that the alloying approach has reached a plateau of about 300,000 psi tensile strength and that little improvement can be expected from further efforts in this area. Process treatments, such as annealing and ausforming, are able to produce materials having tensile strengths in the area of about 450,000 psi; however, processes of this tye are restricted in applicaton and are relatively expensive. Ultrahigh strength wire, having a tensile strength of about 500,000 psi, has been produced, but again this particular development is limited in its applications.
It is generally known that if it were not for lattice defects in the crystal structure, the strength of polycrystalline materials would be in the range of millions of psi. Theoretically, iron should not plastically deform under stresses less than about 2,000,000 psi. However, due to the crystalline defects such as dislocations, iron will plastically deform at stresses as low as 30,000 psi. To explain and hopefully control the impact of these crystalline defects many theories have been developed and are now being used in a continuing effort to produce higher strength materials.
One of the most promising theories is that based on dislocations and their control. One type of dislocation is a line defect in the crystal lattice structure. It is postulated that dislocations of unlike orientation often interact to form a more regular crystal structure. Such interactions have the net effect of annihilating dislocations.
Based on this knowledge, the effects of many processes have been theoreticaly explained in terms of their ability to modify the distribution and density of dislocations and the impact of these modifications on the physical and/or chemical properties of a polycrystalline material. Examples include work hardening which results in the accumulation of dislocations at barriers in the crystalline structure, and annealing which has the effect of reducing the number of dislocations by promoting the aforementioned combination of dislocations. Unfortunately these processes are quite expensive both in terms of the equipment required and of the energy consumed.
In the efforts which led to this invention, special attention was given to improving the life of tools made from materials such as T-15 tool steel and the corrosion resistance of steel alloys, especially stainless steel. These efforts were guided by a theory that a relatively low cost cryogenic-magnetic treatment could be used to improve these and many other properties of ferromagnetic materials.